Illuminator and image reading device and image forming apparatus having the same

ABSTRACT

An image forming apparatus employing an illuminator configured to irradiate light to a photosensitive body to change a level of electrical potential of the photosensitive body. The illuminator includes at least one light source configured to generate light and a light guide configured to guide the light received from the light source toward the photosensitive body. The light guide includes at least one incidence face and an emission face. The at least one incidence face faces the light source in a main scanning direction to receive the light from the light source into the light guide. The light exits from the light guide through the emission face toward the photosensitive body. The emission face includes a diffusion pattern having a plurality of semi-cylindrical structures along a width direction of the light guide. A radius of curvature of the semi-cylindrical structures increases away from the at least one light source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 13/725,181,filed Dec. 21, 2012, which is a Continuation of U.S. patent applicationSer. No. 12/606,434 which claims the benefit of Korean PatentApplication No. 10-2009-0002958, filed on Jan. 14, 2009 in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein by reference in its entirety.

BACKGROUND

1. Field

The present disclosure relates generally to an illuminator and, moreparticularly, to an illuminator having a light guide to guide lightgenerated from a light source to an object to be illuminated, and to animage reading device and image forming apparatus employing suchilluminator.

2. Description of the Related Art

An image reading device is provided in a variety of electronicappliances, such as digital scanners, copiers, facsimiles, and the like,as well as devices combining some of the functions thereof, and servesto read image information recorded on a document.

Generally, an image reading device may include an illuminator toirradiate light to a document, an image sensor to sense the lightreflected from the document, and an optical system to guide thereflected light from the document to the image sensor. The illuminatormay include a light source to generate light and a light guide to guidethe light generated from the light source toward the document.

An illuminator with a light guide is also often used as a chargeeliminator to eliminate or reduce electric potential remaining on asurface of a photosensitive body provided in an electro-photographicimage forming apparatus, such as, for example, a laser printer and adigital copier.

To assure good performance of the image reading device and/or the chargeeliminator, an illuminator desirably irradiates light uniformly or nearuniformly in the main scanning direction and/or in the sub scanningdirection.

SUMMARY

According to an aspect of the present disclosure an illuminator may beprovided to include at least one light source configured to generatelight and a light guide including at least one incidence face facing thelight source and an emission face configured to emit the light to atarget object. A diffusion pattern may be formed on the emission face toextend from one longitudinal end to the other longitudinal end of theemission face.

The emission face may have a constant cross section along thelongitudinal direction thereof. The emission face may alternatively havea cross section that varies along the longitudinal direction thereof.The emission face may be symmetrical about a longitudinal center.

For example, the diffusion pattern may include a plurality ofsemi-cylindrical structures arranged along the width direction of theemission face. A radius of curvature of the plurality ofsemi-cylindrical structures may be constant along the length of theemission face or it may alternatively increase or decrease from thelongitudinal end to or near the center of the light guide.

The at least one light source may include a first light source thatfaces one end surface of the light guide and a second light source thatfaces the other end surface of the light guide. The light source mayinclude a light emitting diode (LED).

According to another aspect, an image reading device may be provided toinclude a reading device body within which a reading unit is installed.The reading unit may include an illuminator, a moving optical system andan image sensor. The illuminator may be configured to move in a subscanning direction, and may be configured to irradiate light onto adocument in a main scanning direction. The moving optical system may beconfigured to move in the sub scanning direction relative to theilluminator. The image sensor may be configured to receive the lightreflected from the document, and may be configured to convert thereceived light into electric signals. In one example, the illuminatormay include a plurality of light sources arranged along the sub scanningdirection and a plurality of light guides arranged to correspond to theplurality of light sources. The plurality of light guides may beconfigured to irradiate light to different regions of the document alongthe sub scanning direction.

According to yet another aspect, an image forming apparatus may beprovided to include an illuminator for irradiating light to aphotosensitive body for removal of electric potential. The illuminatormay include at least one light source to generate light and a lightguide to guide the light of the light source to the photosensitive bodyThe light guide may include at least one incidence face facing the lightsource in a main scanning direction and an emission face that emitslight to the photosensitive body. A diffusion pattern may be formed onthe emission face and extends from one end to the other end of theemission face in the main scanning direction.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features and advantages of the disclosure will become moreapparent by the following detailed description of several embodimentsthereof with reference to the attached drawings, of which:

FIG. 1 is a view illustrating a configuration of an image formingapparatus according to an embodiment;

FIG. 2 is a view illustrating the configuration of a reading unitreading device according to an embodiment usable in an image;

FIG. 3 is a perspective view illustrating a light source and a lightguide included in an illuminator according to an embodiment;

FIG. 4 is a sectional view taken along the line I-I of FIG. 3;

FIG. 5 is a sectional view taken along the line II-II of FIG. 3;

FIG. 6 is a sectional view illustrating a light guide according toanother embodiment;

FIG. 7 is a view illustrating a configuration of an illuminatoraccording to an embodiment;

FIG. 8 is a graph illustrating distribution of light quantity on adocument plane based on the arrangement of the light source and lightguide as shown in FIG. 7; and

FIG. 9 is an enlarged view illustrating a developing device of FIG. 1.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. While the embodiments are described with detailedconstruction and elements to assist in a comprehensive understanding ofthe various applications and advantages of the embodiments, it should beapparent however that the embodiments can be carried out without thosespecifically detailed particulars. Also, well-known functions orconstructions will not be described in detail so as to avoid obscuringthe description with unnecessary detail. It should be also noted that inthe drawings, the dimensions of the features are not intended to be totrue scale and may be exaggerated for the sake of allowing greaterunderstanding.

With reference to FIG. 1, an image forming apparatus 1 is schematicallyillustrated. As shown in FIG. 1, the image forming apparatus 1 mayinclude an image reading device 2 configured to read an image recordedon a document and a printing device 3 configured to print the image onpaper or another medium.

The image reading device 2 may include a reading device body 10 thatincludes a reading frame 12 and a cover 14. The cover 14 may bepivotally and/or rotatably coupled to the reading frame 12 to open orclose an upper surface of the reading frame 12. The cover 14 may beprovided with an automatic document feeder (ADF) 30 that may beconfigured to feed documents to enable, for example, multiple scanningoperations in succession.

A document tray 16 and an ADF glass 18 may be installed and provided atan upper surface of the reading frame 12. The document tray 16 may beconfigured to allow for a user to place documents thereon, sheet bysheet, for example. The ADF glass 18 may be provided and configured toallow the user to read documents delivered by the ADF 30.

A reading unit 20, configured to read information recorded on adocument, may be provided in the reading frame 12. The reading unit 20may be configured to read image information recorded on a documentplaced on the document tray 16 or on a document delivered by the ADF 30by irradiating light to the document, by detecting light reflected fromthe document and by converting a detected quantity of the light intoelectric signals.

The ADF 30 may include a document inlet 31 into which a document to beread is introduced, a document outlet 32 from which a read document isdischarged, a document delivery path 33 defined in the interior of thecover 14 for document delivery, and various rollers arranged andconfigured on the document delivery path 33 for document delivery.

The document inlet 31 may be installed and positioned at one side of thecover 14, while the document outlet 32 may be installed and positionedunder the document inlet 31, for example. A document feed tray 34 may beprovided near the document inlet 31, on which documents to be deliveredby the ADF 30 may be loaded. Also, a document discharge tray 35 may beprovided near the document outlet 32, on which documents discharged fromthe document outlet 32 may be loaded and/or received.

The document delivery path 33 may have, according to an embodiment, anapproximated C-shaped form. One end of the document delivery path 33 maybe connected to the document feed tray 34 through the document inlet 31,while the other end of the document delivery path 33 may be connected tothe document discharge tray 35 through the document outlet 32. Thedocument delivery path 33 may alternatively comprise other forms orshapes.

The rollers for document delivery may include, but are not limited to, adocument pickup roller 36 configured to pick up the documents loaded onthe document feed tray 34; first, second and third delivery rollers 37,38 and 39 configured to deliver the documents picked-up by the documentpickup roller 36 along the document delivery path 33; and a documentdischarge roller 40 configured to discharge the read documents to thedocument discharge tray 35. The first delivery roller 37 closest to thedocument pickup roller 36 and an optional frictional pad 41 may functionand be configured to separate the documents picked-up by the documentpickup roller 36 into individual sheets. The optional frictional pad 41may be installed and provided opposite the first delivery roller 37.

Referring to FIG. 2, a schematic representation of the reading unit 20included in the image reading device 2 is shown according to anembodiment. The reading unit 20 may include an illuminator 50, a movingoptical system 60, a condensing lens 70 and an image sensor 80.

FIG. 3 provides a perspective view of a light source and a light guidecapable of being utilized in the illuminator 50 according to anembodiment.

The illuminator 50 may be configured to irradiate light to a documentalong a main scanning direction (designated by the arrow X as shown inFIG. 3) to enable document reading. When located under the ADF glass 18,the illuminator 50 irradiates light to a document delivered by theautomatic document feeder 30. When located under the document tray 16,the illuminator 50 irradiates light to a document placed on the documenttray 16.

The illuminator 50 may include a first carriage 51 movably installed ina sub scanning direction (designated by the arrow Y as shown in FIG. 2)and may be configured to irradiate light to a document D placed on thedocument tray 16 while moving along the sub scanning direction Y. Thefirst carriage 51 may include one or more light sources 52 and/or 53, alight guide 90, and a reflecting mirror 54. The light guide 90 may beconfigured to guide light generated from the light sources 52 and/or 53toward the document D.

The moving optical system 60 may include a plurality of reflectingmirrors, such as reflecting mirrors 61 and 62, to guide the lightreflected from the document D to the image sensor 80. The reflectingmirrors 61 and 62 may be mounted on a second carriage 63, which may beinstalled to be movable along the sub scanning direction Y.

The illuminator 50 and the moving optical system 60 may be adapted andconfigured to be moved at different speeds in the sub scanning directionto maintain a constant length of the total optical path. When theilluminator 50 irradiates light to the document D while moving at aspeed V, for example, the moving optical system 60 may be moved at aspeed V/2 to reflect the light emitted from the illuminator 50 to theimage sensor 80. Both the illuminator 50 and moving optical system 60may be driven by a drive mechanism including, for example, a drivemotor, pulley and/or wire (not shown).

The condensing lens 70 and the image sensor 80 may be kept at fixedpositions in the reading device body 10. The condensing lens 70 may belocated in front of the image sensor 80 based on the optical path tofocus the light reflected from the moving optical system 60 on the imagesensor 80.

The image sensor 80 may be configured to receive and convert the lightreflected from the document D into electric signals. The image sensor 80may be a Charge Coupled Device (CCD) image sensor or a ComplementaryMetal Oxide Semiconductor (CMOS) image sensor, for example. The imagesensor 80 is not limited to any particular type of image sensor. In thecase of a high-speed image reading device capable of reading a documentof a size greater than, for example, A3 size, it may be desirable toadopt a CCD image sensor having a greater resolution and depth of focus,for example.

The image sensor 80 may be configured such that different color sensors,for example, red, green and blue sensors, are arranged in rows on a percolor basis.

FIG. 4 is a sectional view taken along the line I-I of FIG. 3, and FIG.5 is a sectional view taken along the line II-II of FIG. 3.

As shown in FIGS. 2 to 5, the light guide 90 of the illuminator 50 maytake the form of a bar having a longitudinal direction corresponding tothe main scanning direction X and a width direction corresponding to thesub scanning direction Y. The light guide 90 may be made of anacryl-based resin, such as, for example, PolyMethyl MethAcrylate (PMMA),or a transparent synthetic resin, such as, for example, polycarbonate orpolystyrene. The light guide however is not limited to any particulartype of material or substance.

The first light source 52 and the second light source 53 may bearranged, according to an embodiment, at opposite longitudinal sides ofthe light guide 90. Arranging the light sources 52 and 53 at oppositesides of the light guide 90 may enable uniform or near-uniformdistribution of light quantity in the main scanning direction X.

According to an embodiment, the first light source 52 and the secondlight source 53 respectively may include light emitting diodes 52 a and53 a. The first light source 52 and the second light source 53 mayinclude, for example, white light emitting diodes. Although FIG. 3illustrates the light sources 52 and 53 as being respectively arrangedat opposite sides of the light guide 90, it is also possible to providea single light source at one side of the light guide 90. Otherconfigurations are also possible.

The light guide 90 may include incidence faces 91 and 92, a reflectingface 93, guide faces 94, and an emission face 95. In an embodiment, thelight, generated from the light sources 52 and 53, is introduced intothe light guide 90 via the incidence faces 91 and 92 and is guidedtoward the emission face 95 via the reflecting face 93 and guide faces94 to thereby be emitted out of the light guide 90.

The incidence faces 91 and 92 may be defined at opposite longitudinalend surfaces of the light guide 90, respectively, to face the firstlight source 52 and second light source 53. If a light source isprovided at only one longitudinal end surface of the light guide 90, theother end surface of the light guide 90 that does not face the lightsource may be provided with a reflecting structure (for example, areflecting coating and/or a reflecting plate).

The reflecting face 93 reflects the light introduced into the lightguide 90 via the incidence faces 91 and 92 toward the emission face 95.The reflecting face 93 may include a plurality of reflecting patterns 93a arranged in the main scanning direction. Although FIG. 4 illustratesthe reflecting patterns 93 a in the form of prisms, semi-cylindrical,semi-spherical, or other lens-shaped reflecting patterns are alsopossible.

The guide faces 94 may be configured to guide the light reflected fromthe reflecting face 93 toward the emission face 95. The guide faces 94may define opposite lateral surfaces of the light guide 90 arranged inthe sub scanning direction Y, the guide faces 94 being inclined in sucha manner that a width of the light guide 90 increases from thereflecting face 93 to the emission face 95, in an embodiment. With theinclined guide faces 94, it may be possible to effectively prevent lossof light from the light guide 90 when the light reflected by thereflecting patterns 93 a is deflected in the width direction Y of thelight guide 90.

The emission face 95 may be arranged opposite the reflecting face 93 andmay be configured to emit the light guided via the reflecting face 93and guide faces 94 toward the document D. The emission face 95 may havea predetermined curvature.

The emission face 95 may be provided with a diffusion pattern 96extending from one end 95 a to the other end 95 b of the emission face95 in the longitudinal direction X, for example. The diffusion pattern96, as shown in FIGS. 3 and 5, may include a plurality ofsemi-cylindrical structures 97 arranged in the width direction Y of theemission face 95. The diffusion pattern 96 however is not limited to thesemi-cylindrical structures 97, and other structures, patterns, orshapes may be utilized.

The diffusion pattern 96 diffuses the light to be emitted from theemission face 95 to enable mixing of adjacent light beams, thus enablinguniform or near-uniform irradiation of light in the sub scanningdirection Y. Accordingly, if, for example, a reading position on adocument or an image forming position on the image sensor is displacedfrom an initial design position due to, for example, characteristics ofthe optical system or an assembly tolerance of optical elements, it ispossible to prevent deterioration in reading performance.

For example, in the case of the image reading device 2 as shown in FIG.2 wherein the illuminator 50 and moving optical system 60 are moving atdifferent speeds, if an installation angle between the two reflectingmirrors 61 and 62 has a tolerance of about 0.5 degrees rather than beingaccurately 90 degrees, a reading position on an A3-size document may bedisplaced by about 4 mm in the sub scanning direction Y. In this case,as the illuminator 50 uniformly or near uniformly irradiates light overa predetermined region of the document in the sub scanning direction Y,it is possible to prevent deterioration in reading quality despite thedisplacement of the reading position on the document.

Further, according to an embodiment, it is noted that the diffusionpattern 96 longitudinally extending throughout the emission face 95 mayallow the illuminator 50 to uniformly or near uniformly irradiate lightin the main scanning direction X. If the diffusion pattern 96 is formedon only a partial longitudinal region of the emission face 95, aboundary between a region having the diffusion pattern 96 and a regionwithout the diffusion pattern 96 may experience sudden change in lightirradiation characteristics, thus resulting in deterioration in readingquality.

The emission face 95 provided with the diffusion pattern 96 may have aconstant cross section in the longitudinal direction X and also may besymmetrical in the longitudinal direction X. The symmetric emission face95 may be desirable when the light sources 52 and 53 are provided atopposite sides of the light guide 90.

Although FIG. 5 illustrates the semi-cylindrical structures arranged inthe sub scanning direction Y as having the same radius of curvaturealong the light guide 90, semi-cylindrical structures having differentradiuses of curvature at different portions of the light guide 90 arealso possible.

For example, FIG. 6 is a sectional view of a light guide 90 a accordingto another embodiment. As shown in FIG. 6, a diffusion pattern 96 a mayhave varied cross sections along the longitudinal direction of the lightguide 90 a. In FIG. 6, the solid line illustrates a first part 98 a of asemi-cylindrical structure 98 adjacent to a light source 55, and thedotted line illustrates a second part 98 b of the semi-cylindricalstructure 98 in or near the center of the light guide 90 a.

The second part 98 b in or near the center of the light guide 90 a mayhave a radius of curvature larger than that of the first part 98 a ofthe light guide 90 a adjacent to the light source 55, for example. In aregion of the light guide 90 a adjacent to the light source 55, thelight emitted from the emission face 95 of the light guide 90 a may beconcentrated in the sub scanning direction Y. It may thus be desirablethat a radius of curvature of the first part 98 a of thesemi-cylindrical structures 98 adjacent to the light source 55 besmaller than that of the second part 98 b, in order to increase adiffusion angle of light. To prevent loss of light due to excessivediffusion of light in or near the center of the light guide 90 a, it maybe desirable that a radius of curvature of the second part 98 b of thesemi-cylindrical structure 98 be larger than the first part 98 aadjacent to the light source 55.

The cross section of the diffusion pattern 96 a may vary in thelongitudinal direction of the light guide 90 a, for example, to preventunusual or undesirable change in the distribution of light quantity at aspecific position of the emission face 95.

It should also be noted that although the above embodiments describe thediffusion pattern having semi-cylindrical structures by way of example,a diffusion pattern of prismatic or other structures is also possible.

FIG. 7 is a view illustrating a configuration of an illuminator 50 aaccording to an embodiment. As shown in FIG. 7, the illuminator 50 a mayinclude a plurality of light sources 56 and 57 arranged in the subscanning direction Y and a plurality of light guides 90 b and 90 carranged respectively to correspond to the plurality of light sources 56and 57.

The plurality of light guides 90 b and 90 c may be arranged andconfigured to irradiate light to different positions on the document inthe sub scanning direction Y. For example, the first light guide 90 bmay be arranged to irradiate light to a first region A1 of the documentwhile the second light guide 90 c may be arranged to irradiate light toa second region A2 of the document. Although two light sources, 56 and57, along with respective light guides, 90 b and 90 c, are describedwith respect to FIG. 7, additional light sources may also beincorporated in the illuminator.

FIG. 8 is a graph illustrating distribution of light quantity on adocument plane based on the arrangement of the light sources 56 and 57and light guides 90 b and 90 c according to the illuminator 50 a of FIG.7. With the above-described configuration of the illuminator 50 a ofFIG. 7, the graph of FIG. 8 illustrates that based on a sum of lightquantity irradiated to the first region A1 and second region A2 of thedocument, uniform distribution of light quantity may be realized betweena center position C1 of the first region A1 and a center position C2 ofthe second region A2. In FIG. 8, reference letter “G1” designates adistribution curve of light quantity irradiated to the document D fromthe first light guide 90 b, reference letter “G2” designates adistribution curve of light quantity irradiated to the document D fromthe second light guide 90 c, and reference letter “G3” designates adistribution curve of total light quantity irradiated to the document D.

The light guides 90 b and 90 c may be provided respectively at emissionfaces thereof with diffusion patterns 96 b and 96 c, for example, whichextend from one longitudinal end to the other longitudinal end of thelight guides 90 b and 90 c. The diffusion patterns 96 b and 96 c mayrealize uniform or near-uniform distribution of light quantity both inthe sub scanning direction Y and the main scanning direction X. Thedescription of FIGS. 3 to 6 may be applied to the diffusion patterns 96b and 96 c.

With reference again to FIG. 1, the printing device 3 may include apaper supply unit 110, a light scanning unit 120, photosensitive bodies130Y, 130M, 130C, and 130K, a developing unit 140, a transfer unit 160,a fusing unit 170 and a paper discharge unit 180.

The paper supply unit 110 may include a cassette 111 in which paper S,or other printing media, may be stored, a pickup roller 112 configuredto pick up the paper S stored in the cassette 111 sheet by sheet, anddelivery rollers 113 configured to deliver and provide the picked-uppaper toward the transfer unit 160.

The light scanning unit 120 may be configured to irradiate light,corresponding to image information, to the photosensitive bodies 130Y,130M, 130C, and 130K, thereby forming electrostatic latent images onsurfaces of the photosensitive bodies 130Y, 130M, 130C, and 130K.

The developing unit 140 may be configured to feed developer to theelectrostatic latent images formed on the photosensitive bodies 130Y,130M, 130C, and 130K, thereby forming visible images. The developingunit 140 may include four developing devices 140Y, 140M, 140C, and 140Kin which different colors of developers, for example, yellow developer,magenta developer, cyan developer, and black developer, are receivedrespectively. The developing unit 140 is not limited to four developingdevices, and more or fewer developing devices may be incorporated withinthe developing unit 140. Hereinafter, although only the developingdevice 140Y in which the yellow developer is received will be described,it will be appreciated that the following description may applied to theremaining three developing devices 140M, 140C, and 140K.

FIG. 9 illustrates in greater detail the developing device 140Y ofFIG. 1. As shown in FIG. 9, the developing device 140Y may includes acharger 141, a developer storage 142, one or more developer deliverymembers 143, a developing member 144, a waste developer collector 145and a charge eliminator 150.

The charger 141 may be configured to charge the surface of thephotosensitive body 130Y prior to the electrostatic latent image beingformed on the photosensitive body 130Y. The developer stored in thedeveloper storage 142 may be delivered to the developing member 144 byat least one of the one or more developer delivery members 143. Thedeveloping member 144 may be configured to feed the developer to theelectrostatic latent image formed on the photosensitive body 130Y,thereby enabling formation of a visible image.

The visible image formed on the photosensitive body 130Y may betransferred to a transfer belt 161 (shown in FIG. 1). A portion of thedeveloper may remain on the photosensitive body 130Y.

The waste developer collector 145 may be configured to collect wastedeveloper remaining on the photosensitive body 130Y. The waste developercollector 145 may include a cleaning member 146, a waste developerstorage 147 and a waste developer delivery member 148. The cleaningmember 146 removes the waste developer from the photosensitive body130Y, and the removed waste developer is received in the waste developerstorage 147, from where it may be delivered into a separate wastedeveloper container (not shown) by the waste developer delivery member148.

The charge eliminator 150 may be configured to eliminate or reduceelectric potential remaining on the surface of the photosensitive body130Y prior to charging the photosensitive body 130Y. The chargeeliminator 150 may be, for example, a type of illuminator thatirradiates light to the photosensitive body 130Y, and may include alight source 151 and a light guide 152.

The light source 151 may be arranged adjacent to a longitudinal end ofthe light guide 152 (extending perpendicular to the plane of thedrawing). The light guide 152 may comprise an incidence face that facesthe light source 151. The light guide may further include an emissionface that irradiates light passing through the interior of the lightguide 152 to the photosensitive body 130Y.

A diffusion pattern 155 may be provided on the emission face of thelight guide 152 to enable uniform or near-uniform irradiation of lightto the photosensitive body 130Y. The diffusion pattern 155 may extendfrom one longitudinal end to the other longitudinal end of the lightguide 152. The diffusion pattern 155 may include a plurality ofsemi-cylindrical structures arranged in a width direction of the lightguide 152.

The description of FIGS. 3 to 6 may also be applicable to the lightguide 152.

With reference again to FIG. 1, the transfer unit 160 may include thetransfer belt 161, a drive roller 162, a supporting roller 163, one ormore tension rollers 164, and first transfer rollers 165. The transferbelt 161 may rotate while being supported by one or more of the driveroller 162, the supporting roller 163, and the tension rollers 164.

The visible images formed on the respective photosensitive bodies 130Y,130M, 130C and 130K may be transferred to the transfer belt 161, by thefirst transfer rollers 165, to overlap each other. The resulting imageon the transfer belt 161 may be transferred to paper delivered from thepaper supply unit 110 while the paper passes between a second transferroller 166 and the transfer belt 161.

The paper, after having passed through the transfer unit 160, may enterthe fusing unit 170. The fusing unit 170 may include a heating roller171 and a press roller 172. As the paper, on which the image istransferred, passes between the heating roller 171 and the press roller172, the image may be fixed to the paper by heat and pressure.

The paper, after having passed through the fusing unit 170, may beguided to the paper discharge unit 180 to be discharged by one or morepaper discharge rollers 181.

The above-described embodiments provide an image reading device enablinguniform or near-uniform irradiation of light to a document, thusresulting in enhanced image reading performance. Further, when applyingthe uniform or near-uniform irradiation of light to an image formingapparatus, enhanced performance of a charge eliminator may be achieved.

While the disclosure has been particularly shown and described withreference to several embodiments thereof with particular details, itwill be apparent to one of ordinary skill in the art that variouschanges may be made to these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined inthe following claims and their equivalents.

What is claimed is:
 1. An image forming apparatus, comprising: anilluminator configured to irradiate light to a photosensitive body so asto change a level of electrical potential of the photosensitive body;wherein the illuminator comprises at least one light source configuredto generate light and a light guide configured to guide the lightreceived from the light source toward the photosensitive body; andwherein the light guide comprises at least one incidence face and anemission face, the at least one incidence face facing the light sourcein a main scanning direction of the image forming apparatus to receivethe light from the at least one light source into the light guide, thelight exiting from the light guide through the emission face toward thephotosensitive body, the emission face comprising a diffusion patternformed thereon, the diffusion pattern having a plurality ofsemi-cylindrical structures arranged along a width direction of thelight guide, and wherein a radius of curvature of the plurality ofsemi-cylindrical structures becomes increased while getting farther awayfrom the at least one light source.
 2. The apparatus according to claim1, wherein the emission face is symmetrical about a center along themain scanning direction.
 3. The apparatus according to claim 1, whereinthe at least one light source comprises a first light source facing afirst longitudinal end surface of the light guide and a second lightsource facing a second longitudinal end surface of the light guideopposite the first longitudinal end surface.
 4. The apparatus accordingto claim 1, wherein the at least one light source comprises a lightemitting diode (LED).
 5. The apparatus according to claim 1, wherein thelight guide further comprise a reflecting face and one or more guidefaces, wherein the reflecting face and the one or more guide faces areconfigured to guide the light received through the at least oneincidence face toward the emission face.
 6. The apparatus according toclaim 4, wherein the reflecting face comprises a plurality of reflectingpatterns in the form of prisms.